Radiologic considerations in the adult respiratory distress syndrome treated wih positive end expiratory pressure (PEEP).

Radiographic changes with ARDS are similar to alveolar pulmonary edema in the typical case, although early changes may also be nodular in a small number of cases. These may last about 4 days. Following early alveolar changes the later ARDS findings evolve into a diffuse interstitial pattern, and if the patient survives without complications, the chest x-ray may eventually clear completely. PEEP therapy may cause no x-ray changes or may manifest an apparent hyperinflation appearance to the chest x-ray. PEEP may result in barotrauma changes to the lungs manifested by vesicular rarefactions, lucent lines streaking toward the hilus, radiolucent halos around vessels, pneumatocele formation, and subpleural emphysema manifested by blebs or lucent lines on the chest x-ray. Barotrauma pulmonary changes preceded more serious complications such as pneumothorax, mediastinal emphysema and extrathoracic gas collection.